Site Response in the Bíobío Region, Chile Using the κ Method
Abstract
We assess local site response in the Bíobío region of Chile utilizing seismograms recorded by the Quake-Catcher Network (QCN) micro-electro-mechanical system (MEMS) accelerometers during the aftershock sequence that followed the February 27, 2010 Mw 8.8 Maule earthquake. The earthquakes were captured by over 70 QCN low-resolution (10, 12, and 14-bit) seismometers from March 1 to June 1, 2010. Site effects are caused by the local amplification (or deamplification) of seismic energy due to subsurface structures and geologic materials, which often result in spatially variable patterns of surface damage following an earthquake. In this study we estimate kappa, κ, which models the decay of the acceleration spectra to characterize strong ground motion at high frequencies (> 1 Hz). We calculated the Fourier spectra and κ for each station following the method of Douglas et al. (2010). During the aftershock deployment, the QCN network recorded over 229 earthquakes of magnitude 4.5 and greater. Of these recordings, we determine that 57 earthquakes (25%) have sufficient signal-to-noise quality for use in site response analysis, as determined by visual inspection. Preliminary results indicate κ values between 0.03 and 0.06, with an average value of 0.0407. These values suggest that the Bíobío region of Chile is sharply attenuating and likely consists of less competent rock, as expected. Preliminary results also suggest that kappa does not have a direct correlation with source-station distance; however, this relationship will be investigated more thoroughly as the additional earthquake records from more stations are analyzed. Further comparison of κ values between stations will also highlight the influence of local geology on observed seismic records at individual sites in the Bíobío region. As a result of the site response analysis, we highlight areas of the Bíobío region that may be more susceptible to greater ground shaking following future large earthquakes.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2011
- Bibcode:
- 2011AGUFM.S11A2198L
- Keywords:
-
- 7294 SEISMOLOGY / Seismic instruments and networks;
- 7299 SEISMOLOGY / General or miscellaneous